Assessment of the tear film with tandem scanning confocal microscopy

Purpose: To evaluate the confocal microscopic appearance of the tear film by correlating the interference pattern created by the lipid surface with physiologic measurements of tear function and with clinic diagnosis. Methods. A series of 53 patients was examined with a battery of tests to evaluate the tear film and with confocal microscopy to evaluate the interference pattern created by the lipid surface of the tear film. Assessment of the tear film appearance involved five nonparametric scales: degree of debris in the tear film, variability of the interference pattern over lime, linearity of the interference pattern, number of dry spots seen, and relative thickness of the lipid layer. For 10 other subjects, the confocal appearance of the tear film and evaporation from the ocular surface was tested for before and after meibomian gland expression. Results. The confocal appearance correlated with multiple physiologic variables and clinical diagnosis. Patients with seborrheic meibomian gland dysfunction had a thicker lipid layer, greater variability, and more debris than did patients with obstructive meibomian gland dysfunction. After meibomian gland expression, lipid thickness and linearity increased, whereas pattern variability and evaporation decreased significantly. The mean reduction in evaporation was 48%. Conclusions. Confocal microscopy can be used to examine the tear film, and its appearance correlates significantly with physiologic variables in normal individuals and in disease states. The confocal appearance of the lipid interference patterns and evaporation from the ocular surface are altered after lipid expression from meibomian glands.